zeeboost Posted October 1, 2012 Share Posted October 1, 2012 (edited) I really tried searching and reading the archives to figure this problem out, but I swear I'm about to heave this carburetor into my neighbor's yard. I can't for the life of me pinpoint what's causing it to act up. Small backstory: 8 years ago I purchased a brand new holley 670 street avenger for my 350 (.030, victor jr, holley systemax heads, 9:1 cr, 292hr comp cam). With a little bit of tweaking the engine ran great, a little rich but I was still getting 26 mpg on the highway so no complaints. In 2006 I dropped the car off at a bodyshop; 5 years later I pull it out of the bodyshop incomplete because i was tired of their bs excuses and neglect, and I finally had time to mess with the car again. So for the last few months I've been slowly getting it closer to being on the road again. I picked up a trick kit and used it to rebuild the 670, but it still runs ridiculously rich...like teary-eyed idle rich. If I just drive it doesn the block, it leaves a haze of unburnt fuel. I've torn the carb back apart several times and blew compressed air through every passage, as well as carb cleaner. Everything seems to check out fine, here are my issues of concern: 1) throttle plate bushing has some play in it, enough that when I hook a smoke machine to the carburetor, smoke comes out of it, indicating a small vacuum leak. So I plan on picking up another base plate for the carb, but I doubt that's where my problems are coming from. 2) I have a low vacuum source (5-6") most likely from having too much cam for the engine / compression ratio, but I had the same cam in it before I dropped it off at the bodyshop and like I said, the carb performed just fine with it. I'm wondering if the low vacuum source is causing me to have to open the primary throttle blades too far that it draws in too much fuel. I tried tweaking with the secondary throttle blades but that was a disaster...I just figured I'd try again with the new baseplate. My low profile air filter was interfering with the choke linkage, so the entire choke assembly / plate is removed...don't really need it in texas anyways. I've installed a 3.5 powervalve to make sure it isn't messing with me on the idle circuit, and just for kicks I installed 64 primaries but it still ran stupid rich. Also have another problem with a different carb: So a week ago I picked up a holley 750 4160 off craigslist that was supposed to be a "bolt on and go" carburetor. Lol, well it hydrolocked my engine by dumping in waaay too much fuel, gas literally poured out of cylinders 2 and 4 when I removed the spark plugs. Today I got to messing with the carb and found a blown power valve and baseplate gasket that needed to be changed. Only other thing that I can't figure out is the accelerator pump shoots out the bottom of the carb. As in, no fuel comes out of the squirter on top, but instead I'm assuming the check valve isn't seating beneath the squirter screw, and the gas is just blowing passed it. I've attached a picture of where the fuel is squirting out underneath the carb. Please help with this, I can't tell you how many hours / days I've spent messing with this stupid carburetor to no avail. It's so painful to know my car is just a carburetor adjustment away from being able to drive it on the road again, I just can't figure out what's wrong with it. Edited October 1, 2012 by zeeboost Quote Link to comment Share on other sites More sharing options...
bigbore468 Posted October 1, 2012 Share Posted October 1, 2012 I really tried searching and reading the archives to figure this problem out, but I swear I'm about to heave this carburetor into my neighbor's yard. I can't for the life of me pinpoint what's causing it to act up. Small backstory: 8 years ago I purchased a brand new holley 670 street avenger for my 350 (.030, victor jr, holley systemax heads, 9:1 cr, 292hr comp cam). With a little bit of tweaking the engine ran great, a little rich but I was still getting 26 mpg on the highway so no complaints. In 2006 I dropped the car off at a bodyshop; 5 years later I pull it out of the bodyshop incomplete because i was tired of their bs excuses and neglect, and I finally had time to mess with the car again. So for the last few months I've been slowly getting it closer to being on the road again. I picked up a trick kit and used it to rebuild the 670, but it still runs ridiculously rich...like teary-eyed idle rich. If I just drive it doesn the block, it leaves a haze of unburnt fuel. I've torn the carb back apart several times and blew compressed air through every passage, as well as carb cleaner. Everything seems to check out fine, here are my issues of concern: 1) throttle plate bushing has some play in it, enough that when I hook a smoke machine to the carburetor, smoke comes out of it, indicating a small vacuum leak. So I plan on picking up another base plate for the carb, but I doubt that's where my problems are coming from. 2) I have a low vacuum source (5-6") most likely from having too much cam for the engine / compression ratio, but I had the same cam in it before I dropped it off at the bodyshop and like I said, the carb performed just fine with it. I'm wondering if the low vacuum source is causing me to have to open the primary throttle blades too far that it draws in too much fuel. I tried tweaking with the secondary throttle blades but that was a disaster...I just figured I'd try again with the new baseplate. My low profile air filter was interfering with the choke linkage, so the entire choke assembly / plate is removed...don't really need it in texas anyways. I've installed a 3.5 powervalve to make sure it isn't messing with me on the idle circuit, and just for kicks I installed 64 primaries but it still ran stupid rich. Also have another problem with a different carb: So a week ago I picked up a holley 750 4160 off craigslist that was supposed to be a "bolt on and go" carburetor. Lol, well it hydrolocked my engine by dumping in waaay too much fuel, gas literally poured out of cylinders 2 and 4 when I removed the spark plugs. Today I got to messing with the carb and found a blown power valve and baseplate gasket that needed to be changed. Only other thing that I can't figure out is the accelerator pump shoots out the bottom of the carb. As in, no fuel comes out of the squirter on top, but instead I'm assuming the check valve isn't seating beneath the squirter screw, and the gas is just blowing passed it. I've attached a picture of where the fuel is squirting out underneath the carb. Please help with this, I can't tell you how many hours / days I've spent messing with this stupid carburetor to no avail. It's so painful to know my car is just a carburetor adjustment away from being able to drive it on the road again, I just can't figure out what's wrong with it. Read this thread and take time to view the links; it should help you out... http://forum.grumpysperformance.com/viewtopic.php?f=55&t=264 Quote Link to comment Share on other sites More sharing options...
fastzcars Posted October 1, 2012 Share Posted October 1, 2012 (edited) Maybe the prior owner of the 750 installed the wrong throttle body gasket. I would double check the throttle body gasket to make sure you have the right one for the carb. sounds to me like a passage is being blocked. Edited October 1, 2012 by fastzcars Quote Link to comment Share on other sites More sharing options...
zeeboost Posted October 2, 2012 Author Share Posted October 2, 2012 Read this thread and take time to view the links; it should help you out... http://forum.grumpysperformance.com/viewtopic.php?f=55&t=264 I appreciate the links, but they cover the fundamentals of tuning a properly functioning carburetor...and IMO you really can't start tuning a carburetor until it's acting properly. The primary jets are 64, the powervalve is a new 3.5", new needles and seat, float levels at the very bottom of the sight plug hole, 21* of initial timing, running hotter spark plugs (autolite 3926 with .045" gap), choke has been removed and STILL it idles and drives very rich, leaving a smokey haze everywhere. When I'm purposely leaning out one circuit after another in an attempt to find the problem circuit, and the engine still runs pig rich, this indicates there's a problem going on, something beyond normal tuning. Cold compression is 155-160 on all 8 cylinders, brand new msd 8mm wires / cap / rotor on msd distributor with msd 6a ignition, which is providing plenty of spark. The only thing that I'm having an issue with is the transition circuit, because I have the primary throttle plate open quite a bit since I can't get the secondary plate to adjust and balance the two out. I didn't measure it, but I'm sure my transition slot is exposed at least .050" or more. I'll be messing with that part tomorrow to see if I can get something rigged up for testing purposes. Although I didn't see anything with the smoke machine hooked up, I'll probably replace the intake gaskets anyways for good measure since my idle vacuum is really poor...along with adjusting the valves. But seriously as I'm looking at dropping another $100 on a baseplate when I know there's a very small chance that it's actually the root of the problem, it's pretty tempting to just buy another new carburetor and not have to deal with this bs so I can move forward to the tuning...plus I can get annular boosters instead. The fact though that I've already dropped at least $150-$200 in parts on this 670 and it still doesn't run worth a crap, I'm having a hard time throwing in the towel. Maybe the prior owner of the 750 installed the wrong throttle body gasket. I would double check the throttle body gasket to make sure you have the right one for the carb. sounds to me like a passage is being blocked. I'll double check this tomorrow, but I'm trying to figure out how the base plate gasket would be responsible. If I remove the accelerator pump and put compressed air into the little passage hole that it squirts fuel through, I can feel air coming from each shooter nozzle. However when fuel is added to the equation, it will fill up the body that the shooter nozzle sits in, but instead of squirting out the shooter and squirts out the hole (the one pointed out in the first post) in the bottom of the carb...almost like the check valve under the shooter isn't doing its job. The valve looks fine, but I'm unable to access or even see what it seats up against, so I can't tell if there's a bad seal / debris / etc that's keeping it from seating properly. I was hoping someone had experience with this issue before. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted October 3, 2012 Share Posted October 3, 2012 (edited) This article has some great pictures and captions! It might help. But I personally havn't experienced what your dealing with? http://www.superchevy.com/technical/engines_drivetrain/accessories_electronics/sucp_1004_holley_4150_carb_rebuild/viewall.html And this one has some pictures of the layout's on the a holley. I hope you find the issue buddy! http://www.nastyz28.com/~copo/circuits.htm Edited October 3, 2012 by fastzcars Quote Link to comment Share on other sites More sharing options...
zxophile Posted October 3, 2012 Share Posted October 3, 2012 I had a similar issue with Holley carbs in the past, before I embraced fuel injection and Weber carbs, and it was almost always: "1" The wrong gasket in the kit or a flipped gasket that is "upside down". Or "2" In the case of a carb that sat for years, debris or corroded check valve. Holley makes great carbs, but they can be pain chasing down gremlins and it's usually something you thought was fine until you replace it in desperation and suddenly the thing is perfect. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted October 3, 2012 Share Posted October 3, 2012 Go through the net I found this site! it has a boat load of cut away pictures of the inner workings of holley carbs! Im bookmarking this! Here you go! http://www.oldcarmanualproject.com/manuals/Carbs/Holley/H4V-4150-60-80/index.html Quote Link to comment Share on other sites More sharing options...
Michael Posted October 3, 2012 Share Posted October 3, 2012 If the carb ran reasonably well in 2006 and there have been no additions or deletions of components, but after sitting for 5 years the carb is now running poorly, there are two likely culprits: 1. A rubber gasket or O-ring somewhere rotted/frayed/disintegrated. It could be the O-ring in the needle/seat assembly, for example. This happened to me after a similarly long downtime. 2. A fulcrum/pivoting mechanism is binding or otherwise stuck; for example, a stuck float. Quote Link to comment Share on other sites More sharing options...
zeeboost Posted October 4, 2012 Author Share Posted October 4, 2012 (edited) I had a similar issue with Holley carbs in the past, before I embraced fuel injection and Weber carbs, and it was almost always: "1" The wrong gasket in the kit or a flipped gasket that is "upside down". Or "2" In the case of a carb that sat for years, debris or corroded check valve. Holley makes great carbs, but they can be pain chasing down gremlins and it's usually something you thought was fine until you replace it in desperation and suddenly the thing is perfect. Boy you pretty much hit the nail on the head with carburetor #2. I feel foolish for not checking this before, but the gasket that the PO installed between the primary metering block and carb body was wrong, and didn't have a seal for the accelerator pump passage, therefore very little made it into the shooter nozzle area, and most of it dumped underneath the powervalve. Go through the net I found this site! it has a boat load of cut away pictures of the inner workings of holley carbs! Im bookmarking this! Here you go! http://www.oldcarmanualproject.com/manuals/Carbs/Holley/H4V-4150-60-80/index.html I really appreciate your help with finding and sending me these references. There are some very good cutouts and diagrams in here...bookmarked for sure. If the carb ran reasonably well in 2006 and there have been no additions or deletions of components, but after sitting for 5 years the carb is now running poorly, there are two likely culprits: 1. A rubber gasket or O-ring somewhere rotted/frayed/disintegrated. It could be the O-ring in the needle/seat assembly, for example. This happened to me after a similarly long downtime. 2. A fulcrum/pivoting mechanism is binding or otherwise stuck; for example, a stuck float. I replaced the needles and seat and new pieces, and the float can pivot freely. I tried to do as thorough of a cleanup as I could with the carb...before I even began rebuilding it, I disassembled the carb and let each individual section soak for a couple days in seafoam / b12. A little progress, although it's still smokey rich (not as much though): I was finally able to replace the secondary plate set screw with a different one that I could actually adjust. So I opened them up a little, which allowed me to close the primary plate much more to the point that my idle transition slot looked like a square, rather than a looooong rectangle. I set it to about .025" and adjusted the primaries from there to keep my idle. Transition from idle to driving is definately much better. I'll hookup the wideband soon and start logging some AFRs so you can see concrete data versus a vague description. Thanks for the help so far, and I'll keep this thread updated. Edited October 4, 2012 by zeeboost Quote Link to comment Share on other sites More sharing options...
fastzcars Posted October 4, 2012 Share Posted October 4, 2012 I would feel bad. Unless you work with holley carburaters all the time, different gaskets look very much alike! Its very easy to miss very minor differences! Quote Link to comment Share on other sites More sharing options...
fastzcars Posted October 4, 2012 Share Posted October 4, 2012 Sorry I meant to say " I wouldn't feel bad" darn auto correct strikes again on my phone! Quote Link to comment Share on other sites More sharing options...
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